Update ChangeLog and version files for release

ChangeLog

c++tools/ChangeLog

config/ChangeLog

contrib/ChangeLog

contrib/header-tools/ChangeLog

contrib/reghunt/ChangeLog

contrib/regression/ChangeLog

fixincludes/ChangeLog

gcc/BASE-VER

gcc/ChangeLog

gcc/ada/ChangeLog

gcc/analyzer/ChangeLog

gcc/c-family/ChangeLog

gcc/c/ChangeLog

gcc/cp/ChangeLog

gcc/d/ChangeLog

gcc/fortran/ChangeLog

gcc/go/ChangeLog

gcc/jit/ChangeLog

gcc/lto/ChangeLog